1. Field of the Invention
Embodiments of the invention relate to an organic light emitting display supplying a reverse polarity voltage for recovering reliability of pixels to the pixels after power of the organic light emitting display is turned off.
2. Discussion of the Related Art
Each pixel of an organic light emitting display includes an organic light emitting diode (OLED) having a self-emitting structure. The OLED is configured through the stack of organic compound layers including a hole injection layer, a hole transport layer, an emission layer, an electron transport layer, an electron injection layer, etc. The OLED emits light when electrons and holes are combined in an organic layer through a current flowing in a fluorescence or phosphorescence organic thin film.
Each of pixels of an active matrix organic light emitting display includes a driving element and a switching element. The driving element and the switching element are thin film transistors (TFTs) having a metal oxide semiconductor field effect transistor (MOSFET) structure and are formed on a substrate of a display panel. When a reverse bias is applied to the OLED, the OLED does not emit light because the OLED has a polarity. The driving element controls a current flowing in the OLED based on data of an input image. A data voltage of the same polarity is repeatedly supplied to a gate of the driving element in a normal drive mode. However, when the data voltage of the same polarity is repeatedly supplied to the gate of the driving element, a threshold voltage of the driving element is shifted because of a gate bias stress of the driving element resulting from characteristics of the MOSFET structure. Also, the driving element is degraded, and thus reliability of the pixels is reduced. The gate bias stress degrades the driving element and thus reduces life span of the organic light emitting display.